3D Printed Prosthetic Socket For Residual Limb

ABSTRACT

The invention is a 3D printed prosthetic socket for a residual limb consisting of a 3D printed shell. The 3D printed prosthetic socket comprises a distal end adapted for linking the interconnecting adapter of the socket and a proximal end with an opening adapted for inserting the limb. The 3D printed shell comprises a first housing of the socket comprising an inner wall, wherein between the first housing and the second housing, there is an air gap. The distal end adapted for linking an interconnecting adapter of the socket, the first housing and the second housing are made of single 3D printed part, wherein the first housing comprises an elastic region comprising set of shaped openings, and the first housing is connected with the second housing through a reinforcing structure composed of ribs.

TECHNICAL FIELD

The invention relates to a custom-tailored 3D printed prosthetic socketfor a residual limb.

BACKGROUND OF THE INVENTION

High-quality and well-fitting prosthetic sockets are the basis for acomfortable life of a patient with a residual limb. Due to theindividual parameters of each residual limb, it is necessary to makeprosthetic sockets always tailored for the specific patient. Thefunction of the prosthetic socket is both load-bearing, wherein weightis transferred from the residual limb to the prosthesis itself, andfixating, wherein it is necessary to ensure sufficient adhesion of thesocket to the limb, but at the same time the socket needs to becomfortable for the patient. Prosthetic sockets are made with respect tothe condition of the residual limb, the physical activity of the patientand their weight. Since these parameters may change at shorter or longerintervals during the patient's life, it is desirable that themanufacture of the prosthetic socket be as simple as possible and thusless expensive.

Most prior art prosthetic sockets are manufactured in two steps. Thefirst step is to create a model of the residual limb, either manually inform of a casting and a physical model of the residual limb, or adigital CAD/CAM model, from which, in the second step, an individualprosthetic socket is created, most often by lamination or thermoplasticshaping. A disadvantage of these solutions is the time-consuming designand manufacture and the limitation of the design embodiment due to thetechnology used.

Recently, efforts have been made to create 3D printed prosthetic socketstailored for the patient based on a residual limb scan, a residual limbphysical model scan, or residual limb measurements. According to thecurrent state of the art, the digital model of the residual limb ismodified in a computer, and on basis thereof, a CAD model of the socketis created, which is then printed on a 3D printer.

The problem of this solution is, on the one hand, the requirement forsufficient strength of the socket, and, on the other hand, therequirement to ensure comfort for the residual limb for all-day wear.Thus, if the socket is to be strong enough to meet the strengthstandards imposed on sockets, such a socket is uncomfortable for thepatient in case of volume changes of the limb.

In the current state of the art, this problem is solved, for example, inpatent document US20170246013, in which the prosthetic socket consistsof an inner and outer surface, between which there are structuralelastic elements allowing to reduce the pressure of the socket materialon the residual limb. A disadvantage of this solution is the absence ofadaptation of the flexibility of the socket to the specific residuallimb, since each portion of the residual limb includes soft tissues andbone structures differently deforming over time.

In the current state of the art, the lightening of a specific portion ofthe residual limb is solved by inserting soft, for example silicone,pellets to the affected regions. For example, in the patent documentUS20160228266, the lightening of specific portions of a residual limb isdiscussed for greater patient comfort when wearing a prosthesis byinserting soft thinned flexible regions of a residual limb sleeve.

In the current state of the art, there is no outer supporting prostheticsocket that would solve the problem of softening a particular region incontact with the residual limb in 3D printed outer supporting prostheticsockets and that would at the same time meet the requirements forstrength, rigidity, and load-bearing capacity.

SUMMARY OF THE INVENTION

The above shortcomings are, to a certain extent, overcome by a 3Dprinted prosthetic socket according to the present invention thatcomprises a second housing located outside of a first housing connectedto the first housing in the proximal and distal region of the socket,wherein in this manner, an air gap is created between the housings. Thefirst and second housings may be further interconnected by ribs thatprovide additional strength to the prosthetic socket. To removesupporting or unused printing material during the manufacturing process,the first housing, or the second housing, includes at least one opening.

The 3D printed prosthetic socket according to the present inventioncomprises a lightened structure in the distal region designed based onat least one parameter from a set including at least weight of thepatient, degree of their activity, length of the residual limb, geometrythereof, size of the prosthetic foot, type of the prosthetic foot, andtotal length of the prosthesis. Since the distal end comprises asignificant portion of the volume of the socket, by optimizing thelightened structure, the weight of the entire socket is reduced andthereby the comfort of the patient with the residual limb is increasedand material is saved.

The 3D printed prosthetic socket according to the present invention isadapted for connection to the cover of the prosthesis that compriseslinking elements from a set of a pin, opening, spring, groove, helix,clamp joint, thread, screw, and rivet.

In another preferred embodiment, the 3D printed prosthetic socket ismade of one type of material. Alternatively, the 3D printed prostheticsocket according to this invention may be made from two or more types ofmaterials, wherein in this manner, the rigidity of individual regions ofthe first housing of the prosthetic socket may be adjusted.

DESCRIPTION OF DRAWINGS

A summary of the invention is further clarified using exampleembodiments thereof, which are described with reference to theaccompanying drawings, in which:

FIG. 1 shows a transtibial prosthesis comprising a 3D printed prostheticsocket and adjoining prosthetic parts,

FIG. 2 shows a transfemoral prosthesis comprising a 3D printedprosthetic socket and adjoining prosthetic parts,

FIG. 3 shows a cross-sectional view of the 3D printed prosthetic socketwith the first housing comprising openings in the elastic region, and alightened distal end structure,

FIG. 4 shows a detail of the arrangement of the second housing to thefirst housing of the 3D printed prosthetic socket,

FIG. 5 shows the 3D printed prosthetic socket with two housings andopenings of the second housing,

FIG. 6 shows an example of the location of the ribs between the firstand the second housing of the 3D printed prosthetic housing,

FIG. 7 shows a detail of the link of the cover of the prosthesis to the3D printed prosthetic socket,

FIG. 8 shows an implementation of the elastic area by means of elasticelements in a recess in the inner wall of the 3D printed prostheticsocket.

EXAMPLE EMBODIMENTS OF THE INVENTION

Said embodiments show exemplary variants of the embodiments of theinvention, which, however, have no limiting effect on the scope ofprotection.

The prosthetic socket 1 according to the present invention is, as shownin FIG. 1 and FIG. 2, made of a solid material using the 3D printingtechnology, thereby creating a continuous and one-part shell with acavity for the residual limb. In a preferred embodiment, the elasticmodulus of the material used reaches 1,000 to 4,000 MPa at roomtemperature. Alternatively, the prosthetic socket 1 may be made bysimultaneous one-part printing of several types of materials, whereinthe materials may pass continuously or in leaps. In this exemplaryembodiment, the elastic modulus of the first material is 1,000 to 4,000MPa at room temperature and the elastic modulus of another material is 3to 200 MPa at room temperature. In another exemplary embodiment, theprosthetic socket 1 is composed of several portions and thus is not madeof one-part. In this embodiment, at least two portions of the prostheticsocket 1 are connected and secured by a suitable connecting mechanism,wherein at least one portion of the multi-part prosthetic socket 1 ismade by 3D printing technology. The first exemplary embodiment that isshown in FIG. 1 and in FIG. 2, the prosthetic socket 1 comprises adistal end 2 adapted for linking the modular parts 15 of the lower limbprosthesis and a proximal end 4 with an opening for inserting the limb,between which the central portion of the prosthetic socket 1 is located.In another exemplary embodiment, the distal end 2 is adapted for linkingthe prosthetic knee joint 20. In an exemplary embodiment that is shownin FIG. 4, the central portion is made as containing two housings,wherein in a preferred embodiment, the central portion comprises thefirst housing 5 and the second housing 6, between which a free spaceenclosed by these housings is located. The minimum thickness of thefirst housing 5 is 1 mm, the minimum thickness of the second housing 6is 1 mm, and the minimum distance between the first housing 5 and thesecond housing 6 is 1 mm. The prosthetic sockets 1 according to thepresent invention are made on a 3D printer using one of the 3D printingmethods: SLA, SLS, FDM, MJF, DLP, 3DP, PJF, CLIP. One or more materialsof which the prosthetic socket 1 is made belongs to the set of PA, ABS,PLA, PE, PP, CPP, HPP, TPU, TPE, photopolymers, and other materialssuitable for the above-mentioned 3D printing methods. The chosenmaterial may also be reinforced using fibers of glass, carbon, carbonnanofibers, or any other suitable fibers.

Regardless of the embodiment of the central portion, the prostheticsocket 1 comprises an inner wall 7 that is in contact with the limb andhas a load-bearing and a lightening function, and a rigid wall 8 thathas a load-bearing and aesthetic function and, furthermore, is arepresentation of the outer shape of the socket of the prosthesis andsimultaneously is adapted for shape alignment of the prosthesis withregard to the offset of the limb relative to the axis of the prosthesis.The central longitudinal axis of the inner space of the prostheticsocket 1 corresponds to the axis of the limb, and the centrallongitudinal axis of the outer surface follows the axis of theprosthesis. The relative position of the axis of the inner space and theaxis of the outer space is different in most patients, wherein thecentral longitudinal axis of the inner space and the central axis of theouter space form an angle from the set of 0° to 90°, but most often 0°to 45°. In some patients, the axes are identical and the solutionaccording to this invention may be applied to these cases as well.

The prosthetic socket 1 is adapted for transferring the load from thelimb to the axis of the prosthesis connecting the prosthetic socket 1 tothe prosthetic foot 19. Due to the anatomy of the structure of the limb,it is necessary to lighten some of its regions, i.e. allow their shapeand volume expansibility and provide space for possible swelling andprevent unwanted soft tissue bruising. This is achieved by including atleast one elastic region 10 in the structure of the prosthetic socket 1that achieves a maximum of 85% of the rigidity of the rigid region 9 atroom temperature. In a preferred embodiment, the rigidity of the elasticregion 10 is in the range of 5% to 85% of the rigidity of the rigidregion 9 at room temperature. Alternatively, the prosthetic socket 1comprises two elastic regions 10, in the posterolateral andposteromedial region. In another exemplary embodiment, the elasticregion 10 of the socket may be located in the posterior region, anteriorregion, medial region, or lateral region. In another exemplaryembodiment, the central portion comprises, arbitrarily according to theindividual proportions of the patient, the residual limb, or thestructure type of the prosthetic socket 1, the elastic regions 10. In anexemplary embodiment, in which the prosthetic socket 1 is made ascontaining two housings, only the first housing 5 comprises the elasticregion 10. In this exemplary embodiment, the second housing 6 ishermetically sealed and its rigidity reaches at least 90% of therigidity of the material used at room temperature. In an exemplaryembodiment shown in FIG. 5, the second housing 6 comprises at least oneopening 13 of the second housing that is of any shape, wherein theopening 13 of the second housing is adapted for moisture removal,aeration of the prosthetic socket 1 to the limb, removal of excessmaterial during manufacture, reducing the weight of the second housing6, or it has an aesthetic function, or it is adapted for placement of avacuum valve, lock, or another fastening mechanism, or is adapted forany combination of the functions listed.

In the first exemplary embodiment, the elastic region 10 comprises a setof shaped openings 14. An exemplary embodiment of the shaped openings 14is shown in FIG. 3, wherein the shaped openings 14 may also be mutuallyinterconnected and thus form more complex shapes. The openings may alsohave additional other various shapes fora defined purpose. Depending onthe specific shape, distance, and size, the shaped openings 14 reducethe rigidity of the elastic region 10 and provide it with directionalexpansibility. In a preferred embodiment, the elastic region 10 issimultaneously expansible in multiple directions, i.e. it has a negativePoisson's number value. In one of the exemplary embodiments, all shapedopenings 14 of the set have the same shape and their size and distancechange continuously, wherein their sizes increase towards the centre ofthe elastic region 10. In alternative embodiments, it is possible tocombine different shaped openings 14 and arbitrarily change their sizeand distance independent of the position in the elastic region 10.Alternatively, it is possible to make the elastic region 10 using ashaped recess in the inner wall 7 of the prosthetic socket 1, as shownin FIG. 8. In this embodiment, elastic elements 12 are located in therecess in the inner wall 7 which, depending on the shape, size, andinner structure, spring under load. In this exemplary embodiment, therequired lower rigidity of the prosthetic socket 1 and a lower load onthe limb are achieved in the location of the elastic elements 12.

The rigidity of the regions 9,10 is determined by the specific shape,distance, and size of the shaped openings 14 located in the givenregion. In the case of the rigid regions 9, the shaped openings 14 aresmaller, they have a shape that ensures a greater rigidity of the rigidregion 9, and/or they are spaced from each other, or the shaped openings14 are not located in the rigid regions 9 at all. Using this embodimentof the shaped openings 14, thicker 3D printed structures are achievedthat fill the space between the shaped openings 14, while ensuring ahigher rigidity of the rigid region 9. By thicker 3D printed structuresare meant structures with a larger cross-section at the location betweenthe shaped openings 14 and with a severalfold higher volumerepresentation in proportion to the volume representation of the shapedopenings 14. In the case of the elastic regions 10, the shaped openings14 are bigger, they have a shape that ensures a lower rigidity of theelastic region 10, and/or they are located in proximity to each other.Using this embodiment of the shaped openings 14, thinner 3D printedstructures are achieved that fill the space between the shaped openings14, while ensuring a lower rigidity of the elastic region 10. By thinner3D printed structures are meant structures with a smaller cross-sectionat the location between the shaped openings 14 and with a severalfoldlower volume representation in proportion to the volume representationof the shaped openings 14, wherein they supply the required elasticityto the elastic region 10 if the limb in the prosthetic socket 1 exertsforce on it.

The transfer of the load at the distal end 2 of the socket of theprosthesis 1 is implemented using a lightened structure 11 shown in FIG.3. It is designed using a finite element method by calculating theoptimal material distribution with respect to the prosthesis geometryand the total transferred load. This load is based on the individualparameters of each patient, wherein the individual parameters are from aset comprising at least the patient's weight, physical activity, lengthof the limb, limb geometry, size of the prosthetic foot 19, type of theprosthetic foot 19, and the total length of the prosthesis thatcomprises the prosthetic socket 1, a linking adapter 3, modular parts 15of the prosthesis, and the prosthetic foot 19, wherein in anotherexemplary embodiment, it also comprises the cover 17 of the prosthesis.In another exemplary embodiment, the prosthesis also includes the kneejoint 20. The embodiment of the lightened structure 11 itself isdesigned also with regard to the need of removal of unnecessary materialafter the 3D printing, therefore, it does not comprise any enclosedspace from which unused printing material could not be removed aftermanufacture.

The distal end 2 of the prosthetic socket 1 is adapted for linking thelinking adapter 3, wherein the linking adapter 3 is further connected tothe modular parts 15 of the prosthesis which are further connected tothe prosthetic foot 19. In a preferred embodiment, the linking adapter 3is firmly connected to the prosthetic socket 1, wherein the modularparts 15 of the prosthesis are detachably linked to the linking adapter3. The linking adapter 3 may be linked to the 3D printed prostheticsocket 1 using, for example, screws, snap-in mechanism, or thread, wherethe 3D printed prosthetic socket 1 comprises an outer thread and thelinking adapter 3 comprises an inner thread, or the 3D printedprosthetic socket 1 comprises an inner thread and the linking adapter 3comprises an outer thread.

In the first exemplary embodiment, the prosthetic socket 1 is linked tothe other portions of the prosthesis using a screw connection, whereinin this exemplary embodiment, the distal end 2 contains at least oneopening for the thread. Alternatively, other structural joints may beused, such as, for example, nails, threaded inserts, pins, screws,lamellae, connecting fittings, or also gluing.

In one of the exemplary embodiments, the prosthetic socket 1 comprisesthe distal end 2 and the proximal end 4, between which a central portionis located comprising the first housing 5 and the second housing 6. Inthis exemplary embodiment, between the first housing 5 and the secondhousing 6, a reinforcing structure composed of ribs 16 is located, as isshown in FIG. 6.

In an exemplary embodiment shown in FIG. 7, an assembly of theprosthetic socket 1 with the cover 17 of the prosthesis is shown. Inthis exemplary embodiment, the prosthetic socket 1 comprises a linkingelement 18 for linking the cover 17 of the prosthesis. The cover 17 ofthe prosthesis is continuous and one-part and is made of a solid orelastic material using the 3D printing technology. The function of thecover 17 of the prosthesis is aesthetic, wherein it covers the modularparts 15 of the prosthesis, in another exemplary embodiment, it alsocovers the knee joint 20. In this exemplary embodiment, the cover 17 ofthe prosthesis comprises, from the inner side of the edge for linking tothe prosthetic socket 1, at least one element adapted for connecting tothe linking element 18, wherein it is an opening, groove, or any otherelement corresponding, in terms of its shape, to the outer surface ofthe linking element 18. In this exemplary embodiment, the linkingelement 18 is a pin of approximately cylindrical shape, perpendicular tothe inner wall 7 of the cover 17 of the prosthesis. Alternatively, thelinking element 18 is embodied as a spring, clamp, at least 1 mm highedge, perpendicular to the inner wall 7 of the cover 17 of theprosthesis, diminishingly tapered edge of the cover 17 of theprosthesis, or as any other suitable dismountable joint. In thisexemplary embodiment, the prosthetic socket 1 comprises a recesscorresponding to the size and thickness of the edge of the wall of thecover 17 of the prosthesis, wherein their connection creates a seamlessjoint that does not create any overlap between the socket 1 and thecover 17 of the prosthesis.

The manufacture of the 3D printed prosthetic socket 1 according to thepresent invention is implemented using a system of a communicativelyinterconnected 3D scanner, computer device, and 3D printer, and itcomprises a step of obtaining the digital image of the residual limb,step of adjusting the area of the digital image of the residual limb,and a design of the shell of the prosthetic socket 1, and a step ofmanufacturing the prosthetic socket 1 on a 3D printer.

LIST OF REFERENCE NUMBERS

-   1—prosthetic socket-   2—distal end-   3—linking adapter-   4—proximal end-   5—first housing-   6—second housing-   7—inner wall-   8—outer wall-   9—rigid region-   10—elastic region-   11—lightened structure-   12—elastic element-   13—opening of the second housing-   14—shaped opening-   15—modular parts of the prosthesis-   16—ribs-   17—cover of the prosthesis-   18—linking element-   19—prosthetic foot-   20—prosthetic knee joint

1-7. (canceled)
 8. A 3D printed prosthetic socket for a residual limbconsisting of a 3D printed shell comprising a distal end adapted forlinking an interconnecting adapter of the socket and a proximal end withan opening adapted for inserting the limb, wherein the shell comprises afirst housing of the socket comprising an inner wall and a secondhousing comprising an outer wall of the prosthetic socket, wherein thesecond housing is located outside of the first housing and the firsthousing and the second housing are connected at the distal end of theprosthetic socket and at the proximal end of the prosthetic socket,wherein there is an air gap between the first housing and secondhousing, and the distal end adapted for linking an interconnectingadapter of the socket, the first housing and the second housing are madeof single 3D printed part, wherein the first housing comprises anelastic region comprising set of shaped openings, and the first housingis connected with the second housing through a reinforcing structurecomposed of ribs.
 9. The 3D printed prosthetic socket for a residuallimb according to claim 8, wherein the shaped openings are adapted toreduce the rigidity of the elastic region and provide it withdirectional expansibility, wherein the elastic region has a negativePoisson's number value.
 10. The 3D printed prosthetic socket for aresidual limb according to claim 8, wherein the second housing comprisesopenings of the second housing.
 11. The 3D printed prosthetic socket fora residual limb according to claim 8, wherein the shell comprises atleast one elastic region comprising a set of at least three elasticelements.
 12. The 3D printed prosthetic socket for a residual limbaccording to claim 8, wherein the shell of the prosthetic socket is madeof one type of material.
 13. The 3D printed prosthetic socket for aresidual limb according to claim 8, wherein the shell of the prostheticsocket is made of two or more types of materials.
 14. An assembly of the3D printed prosthetic socket for a residual limb according to claim 8and a cover of the prosthesis comprising linking elements from the innerwall of the cover of the prosthesis, wherein the linking element forlinking the cover of the prosthesis to the prosthetic socket is selectedfrom a set of pin, opening, spring, groove, outer helix, inner helix,clamp joint, thread, screw, and interconnecting rivet, and wherein theprosthetic socket is adapted for connection to the linking element.